Asphalt plastisols and process for their preparation



Unite States ASPHALT PLASTESOLS AND PROCESS FOR THEIR PREPARATION Application November 9, 1953 Serial No. 391,126

12 Claims. (til. 208-23) No Drawing.

This invention relates to novel asphalt compositions. More particularly, it is concerned with bituminous plastisols and a method for their preparation.

The termfplastisol is well known in the plastics and coating arts and has reference to a fluid or pasty mixture or suspension of a coating material in particulate form with a plasticizer which is a poor solvent for the resin or polymer at ordinary temperatures, but which is capable of dissolving the particles at elevated temperatures, forming a gel structure. Plastisols have afforded a convenient and economical means of fabricating molded or coated articles from certain restricted classes of thermoplastic resins suchas by spread molding, dip coating, spraying or slush molding. For instance, to make a shaped article, a mold of a desired shape is simply charged with plastisol, heated to cause the plastisol to gel and then cooled, whereupon the plastisol becomes rigid; the article retains the desired shape after removal from the mold;

For certain purposes, e. g., for charging molds or coating cloth it is desirable to employ smooth fluid plastisols whichflow rapidly in order to increase the speedand convenience of the fabricating operation as well as to improve the quality of the fabricated article. More highly viscous plastisols which may in fact be paste-like in consistency are often formed but are generally undesirable.

Heretofore the type of resinous material found most suitable for use in plastisol processes includes especially the polyvinyls, such as polyvinyl chloride. The limitation uponthe process has been the tendency-of most film forming materials when in particulate form of vsuitable subdivision to gradually dissolve in the suspending plasticizers upon storage.

The application of bituminous compositions has always beencomplicated by the viscosity of thev bitumen. Under certain ordinary conditions of temperature it has been possible to overcome this disadvantage by the employment of aqueous asphalt emulsions and the like, controlling the viscosity of the emulsion by a number of well known means, However, such emulsions cannot be'used at'freezing temperatures and requires the transport of large amounts of water. Cutbacks utilizing, rel'atively' volatile thinners are commonly employed. Fire hazards are involved in their use, as well as inefficient utilization of the thinner, which is lost by eventual volatilization.

On the other hand, asphalts sometimesmay be applied at elevated temperatures for the purpose of decreasingtheir viscosity. This has the disadvantage; of requiring hot storage or hot transportation or the presence of heating and melting equipment at the point of application, all-v of such requirements being uneconomical if they can be avoided. Significant limitations on the application of heated asphalts for such purposes as impregnation of roofing felts, are the fire hazard which is always present at such times and skin formation during hot storage.

At. tropical temperatures handling difficulties arise due to the responsibility of fracturing asphalt from shipping drums for the purpose of charging it into melting pots.

It is an object of the present invention to provide improved methods for the application of asphalt for paving, coating, impregnating, or molding purposes. It is another object of this invention to provide stable bituminous plastisols. It is a specific object of this invention to provide such plastisols which are stable over relatively long storage periods. Other objects will become apparent in the following discussion. I

Now in accordance with the present invention it has been found that stable bituminous plastisols may be prepared by suspending solid particles of asphalt having average particle size diameters between about O.5 micron and about 260 microns in hydrocarbon oils of lubricating oil viscosity, the hydrocarbon oil having an aromatic content between about 15% and about 60% by weight. Moreover, the particulate asphalt should possess superficial coatings Whichare resistant to solution in the suspending lubricating oil as moreparticularly discussed hereinafter.

Powdered asphalts have been employed in a number of previous processes, the state of subdivision being largely undetermined. Moreover, in these processes the cutter stocks employed have either been volatile substances, wide range materials which are largely volatile, or aromatic materials which rapidly dissolve the asphalt particles. For some purposes the latter type of composition may be desired, but it is this type of rapid dissolution of the particles at ambient temperatures which the present invention is designedto avoid. Moreover, most of the compositions of the prior art which utilized a preformed mixtureof the flux on or cutter stock together with the powdered asphalt were paste-like in composition and thuspresented numerous problems of uniform application. The same problems of proper impregnation of such items as roofing felts would be present with stiff compositions such aspaste, as are encountered when utilizing ordinary viscous bitumens.

The present compositions, made in accordance with this invention, have beenfound to be highly fluid and in fact to'have a viscosity relatively close tothat of the suspending medium, namely, that of the liquid suspending phase. The advantages of such physical properties will be self evident especially where application to roofing felts or similar articles is contemplated sinceheating will 'not be required to obtain fluidity. The same will be true of application of such plastisols for paving purposes under either hot or cold conditions, e. g., tropical or arctic temperatures.

- The softening point and penetration characteristics are useful guides toward the selection of bitumens which are suitable. In general, asphalts passing the crushing on paper test will have a 0-5 penetration (ASTM D5-25 77 F., IOO-gram load, 5 seconds). With the harder grades of asphalt, it is desirable to modify ASTM D5-25 by employing a temperature of 115 F. and .a ZOO-gram load, insteadof the conventional 77 F. and IOU-gram load. Under such conditions the operable asphalts generally show a 5-35 penetration. In addition to such penetration characteristics, these asphalts will generally be foundto have a 180-240 F. softening point, and it is preferred to employ those with a 180-220 F. softening point. Corresponding coal tar pitches passing said crushing on paper test generally have a l65-240 F. softening point (ASTMD-36-26) and an ASTM D5-25 (77 F., grams, 5 second) penetration of 0-5 and, correspondingly, an ASTM 135-25 F., ZQO-gram, S-sec- 0nd penetration of 0-40.

An example of a suitable 'asphalt'is that produced by taking a 50/60 penetration standard paving grade asphalt, which may contain as, much'as 60% of oil, and steam distilling this asphalt "under'a-high vacuum, e.*g., about a 28-inch vacuum"('2'-inch absolute pressure); for'a long period of time, sufiicient to remove nearly all of the oil.

A satisfactory asphalt of the type employed in our invention has been made in this manner by steam refining the asphalt in a shell still "under high vacuum. In a typical case, a 30 to 40% yield of brittle asphalt is produced, based on the paving grade asphalt charged to the still. Different asphalts will require refinement to different softening points to produce asphalts of the desired brittleness; thus, a typical California asphalt steam refined under high vacuum to a softening point of 200 F. was satisfactory. Other asphalts may require refinemen to a higher softening point, while some asphalts are suitable although refined to a much lower softening point.

Suitable asphalts of the type employed according to this invention, can also be prepared by the solvent re- Asphalts of the type employed according to this invention may also be prepared by airblowing asphaltic and non-asphaltic petroleum residues, with or without the aid of catalysts and oxidizing agents, in accordance with techniques familiar to those skilled in the asphalt refining art. Excellent results are obtainable by steam refininga Midway, California, asphaltic crude to a 150- 160 softening point and to about 05 penetration and then airblowing such residue at a temperature of 400- 500 F. at the rate of 3-5 cubic feet of air per gallon. of charging stock per hour for 16 hours. Naturally, well within the knowledge of those skilled in the art, the length of blowing time and other conditions of operation will vary, in accordance with well-established fining of asphaltic petroleum oil, according to processes principles, according to charging stock employed and widely known and used in petroleum refining. Such soltype of apparatus used.

vent refining which involves the extraction of asphalt is High melting, brittle coal tar pitches, usable in this. advantageous in connection with the practice of this invention, may be obtained in any of the usual coal tar invention for various reasons, included among which is pitch production methods, such as ,in horizontal cokethe easy control of the asphaltic oil content of the as- 20 ovens, gas-Works retorts, blast furnaces, and the like phalt. Solvent extraction of asphalt has been widely de- Among such coal tar pitches successfully employed acscribed in petroleum refining literature. See, for incording to our invention are those having an ASTM stance, Abraham, Asphalts and Allied Substances, D. D36-26 softening point of 165-240" F. and an ASTMv Van Nostrand Co., Inc., New York, 5th ed., pp. 135- 95 D5-25 penetration of 05, and a penetration of 0-40 at 139; Liquid PropaneUse in Dewaxing, Deasp'nalting 115 F., 5 seconds, with a 200-gram load. An ASTM and Refining Heavy Oils, R. E. Wilson, P. C. Keith, Jr., D402 Method distillation of such pitches usually givesand R. E. Haylett, J. Ind. Eng. Chem. 28, 1065 (1936). only a trace of distillate.

Among the solvents employed in the solvent extraction While the particle size may be varied over a con-- of asphalt are liquid sulfur dioxide; liquid hydrocar- 3O siderable range, the most stable plastisols are obtained. bons, such as liquefied ethane, pentane, propane, butane; when the average particle size is between 0.5 and about benzol; toluol; furfural, etc., and mixtures of such $01- 200 microns in diameter. In accordance with the present e t f ex l propane ith I l, invention, dissolution of these particles in the suspending liquid propane has been found to be the most satison is greatly retarded y Superficial treatmqnt of factory solvent in connection with the solvent extraction Particle surfaces- 1 This tftialment y take a l of h l In a typical propane process, propane is of forms and may consntute removal of more soluble liquefied by compression and passed to th bottom of a fractions of the asphalt from the surfaces thereof or deasphalting tower where it flows upward countercurmay Fompnse addltlfm of f' coatmg P rently to descending reduced-asphaltic crude oil. The Phahlc or P l P mammal, having greater reslstaPce liquid propane dissolves the non-asphaltic portion of the 40 lubnFatmg 011 suspending medlum than the bull oil and preferentially precipitates the asphalt. The demmous Pamcles thfimselvesasphalted oil is withdrawn overhead and the asphalt is In,accrdance Wlth h r mvFmlon one form of removed from the bottom of the tower At propane creating the sub ect lubricating oil-resistant surfaces comtemperatures in the range of 100450: F" asphalt is prises superficlal surface extraction of the particulate asonly slightly soluble in the propane, Whereas the remain- Phalt Wlth solvents whlch rerfmve material i m ing components of the reduced-asphaltic crude oil are tenes; preferfibly the f or eXtTaFmg agent largely Soluble therein at such temperatures To extract relatively volatile so that it can be conveniently removed the asphalt from the reduced crude, the reduced crude for recovery of the.extracted material as as the is usually mixed with 4 to 6 times its volume of liquid g Solvents partlculafly Preferred comprise thelower propane at 1204500 R Pressures employed are those ahphatrc hydrocarbons, especially those having between required to maintain the solvent in a liquid state, and abolit 3 about 10 carbon atoms per molecule range from about 100450 Pounds per square inch eluding particularly the pentanes, hexanes, heptanesand mm V octanes and mixtures thereof, such as occur in gasolmes,

Ol-Ldissolving properties of liquid propane for the on naphthas, etc. The most effective hydrocarbons with re- 55 spect to convenience of use and effectiveness of extraction Components of the reduaed Crudfi f theiem' of the desired maltene fraction has been found to be PFramre mes above and 15 accordmg'llf normal hydrocarbons having 6-8 carbon atoms per molesible to regulatethe physical propertles of the precipitated cule, especially 1 heptang asphalt y Varying the Seventy 0f the Oil-dissolving P- In utilizing these extraction solvents, it is preferred that Typical asphalt recoveries y the p p extraction so the asphalt particles be mixed with 2-10 volumes of the process are set forth in tabular form below. aliphatic hydrocarbon, based on the volume of the asphalt Charging Stock sfiiffit ggfg Pressure, iiiiie ii rfrif i iliiiii to Charge 0 F p. s. i. a Percent ASTM ASTM Asphalt D525 D36-26 5-3 138 310 45 a 161 as 260 as 0 192 10-1 110 220 25 0 210 4-1 140 320 as 0 176 8-1 120 250 45 0 197 10-1 100 220 25 o 240 E. Texas Crude 8-1 158 380 26.8 5 153 Rhodessa (1a.) Crude. 7. 5-1 350 19.8 4 172 Hvy. Mid-Continent Crude 8. 2-1 161 400 46 4 178 of aliphatic character may be utilized, but the major proportion of suspending oil should be that defined above. Thus, organosol type of compositions are contemplated wherein compatible or non-compatible relatively volatile 8 composition to accelerate coalescence of the asphalt particles with the suspending oil to form essentially a homogeneous asphalt composition having the normal propertiesof asphalts employed for paving, saturation or coat- 1 Calculated from penetration at 77 F.

diluents are used in addition to the oil of lubricating oil ing purposes. The degree of heating required will vary viscosity. Suitable lubricating oil or pale oil fractions quite widely dependent upon the compatibility of the which may .be employed include bulk distillates having asphalt particles with the oil and upon the quantity of a viscosity of from about 100 SUS at 100 F. to about asphalt plastisol to be coalesced. Normally a relatively 300 SUS at 210 F. and may contain aromatics in the low degree of heating is required (e. g., at least 30 secorder of 3060% and flash points above 300 F., par- 10 ondsat at least 200 F.) and it is one of the objects of ticularly where paving grade asphalt compositions are this invention to so design the plastisol that a minimum contemplated. Preferably these fractions are essentially degree of heating is necessary to cause coalescence at non-waxy. Where blown type asphalt compositions are the same time the latter is prevented during reasonably desired, the aromatic hydrocarbon content should be long storage periods at ambient temperatures. For exstill lower, in the order of 30% aromatics. Refer- 15 ample, it is desirable to pass a roofing felt impregnated ence to aromatics is given in terms of ultra violet with the asphalt plastisol through an oven or a tunnel analyses. Suitable lubricating oil fractions, therefore, having infrared lamps of suflicient intensity to cause the comprise bulk lubricating oil distillates or fractions desired coalescence. Where larger structures such as thereof, and lubricating oil raffinates obtained from the pavements and the like are to be treated, open flame type extraction of lubricating oil fractions with selective solof heaters may be utilized although they are not always vents for aromatics such as sulfur dioxide phenol, sulessential. folane, nitrobenzene, furfural, and the like. These Table I 'below summarizes pertinent properties of a raffinates are well known in the art of petroleum refinpulverized Pitch Obtained y a mild thermal Cracking ing. Combinations of extracts and raflinates also are and vacuum flashing of a topped Los Angeles Basin crude suitable. The hydrocarbon lubricating oil may be reoil, the pitch constituting about 12% of the original placed entirely or in part with synthetic lubricants of crude oil residue. It will be noted that a single passage similar viscosity, volatility and solubility characteristics, through a micro pulverizer caused fracturing of the pitch e. g., tetraalkyl silicates, silicones, aliphatic diesters, etc. so that at least 82% passed a 200 mesh screen. A second In preparing the compositions of the present invention, passage through the same pulverizer caused a substantially it is preferred that the suspending oil be employed in greater comminuting of the particles. In order to be proportions from about 25% to about 75 by weight successful, it is desirable that the asphalts utilized in this of the total plastisol. The particulate asphalt should be pr p r i l rly h n r hing hniq re mpresent in amounts between about 75% and 25%, the ployed, have a ring and ball softening point of at least proportion varying with the presence of any additional 200 F. and preferably above about 225 F. desired ingredients such as stabilizers,.pigments, fillers, TABLE I surfactants, suspending agents, and other modifying in- I gredients not essential to the present invention. Prefer- Propemes f ground Puck ably the amount of particulate asphalt is in the order of between about and about based on the total No Pulverized, Pulverized, plastisol composition, the preferred proportion of sus- Grinding lPass 21325588 1 gg fe 1n the eoniugate range o om a out gg Point 322 eve Analysis, passing. The subject plastisols prepared as described above by g jzr addition of the surface treated asphalt particles to the 200 mesh suspending oil with suflicient agitation to cause the fora 1 ,325me811 mation of a relatively stable suspension may be applied p to the desired site by a number of well known means Table II illustrates the properties of paving type asphalt such as spraying, as in the case of paving applications, plastisols. In preparation of these compositions, the or *by application of a uniform amount by use of doctor same particulate asphalt utilized in the above tests was blade technique as in application to roofing felts, fabrics a extracted with either. isopentane or normal heptane so and the like. When utilized for paving purposes, the as to remove approximately 12-25% of the original plastisol may be sprayed on the aggregate either in situ asphalt. This created a lubricating oil-resistant surface or in a mixing apparatus such as a cement mixer. Alterfor the particles making them suitable for the preparanatively, the plastisol may be heated in order to coalesce tion of stable plastisol compositions. The suspending the ingredients prior to application to aggregate or other oil utilized was a bulk distillate having a viscosity of 60 solid base substance. Subsequent to the application of SUS at 210 F. and an aromatic content of about 51% the plastisol, sufficient heat should be applied to the and derived from a mixture of Mt. Poso and Coalinga TABLE 11 Properties of paving type asphalt plastisols Properties of Pitch Properties of Plastisol Properties of Asphalt Solvent Treatment Composition Brookfieid Visa,

Poises at 77 F.

Percent Pen. at Softening Vise, Viscosity Thru 325 77 F Point, poises Reduction mesh Solvent Percent F. F. p Factor, Solvent Pitch Percent Percent 60/210 Initial, Alter V,,/V.,

Ratio, Extracted Pitch Bulk V, 7days ccJg. Dist.

- 03.8.. 41.7 58.3 80 5, 000 230 101 1. 25x10 1, 450 63.8 Isopentane at 77 F 7. 5 1 12 4o 00 020 173 2. 3x10 2,400 63.8 Normalheptane atl15 3 1 25 40 00 4s 77 80 12s 12.0 10 25,000 63.8 do 3/1 25 49 51 210 22 102 210x10 117,000 an 00 3 1 21 i0 00 83 107 104 12s 6.8)(10 8,200

crudes. It will bef'noted "in accordance with the data contained-in Table 11 that imtheabsenc'e o'f any surface treatment of the particles the viscosity o'fthe plastisol rose in one week to about 50 times that of the original composition. On the other 'h'and, when the-washed par- -ticlesfwere employed, the viscosity in one week was relatively unchanged, the best results being obtained with normal heptane. The degree -'of washing *wi11, ef course, vary with the planned durationof storage.

It will be noted} that upon coalescence of these plastisols to for'masubstantially homogeneous asphalt composition, the latter exhibited physical properties typical of good paving grade asphalts.

Table III presents properties of '"plas tisolssuitab1e for the production of blown 'ty'pe 'asphalts such as those especially desired for use in the preparationvof asphalt roofings and the like lt be noted that thesuspending oil in this case constituted mixtures of bulk distillate having a viscosity of 60 210 F. and containing 51% aromaticstogether witha lubricating oil ratfinate obtained by extraction of1 00 FSUS at 1210 F. bulk distillate withfurfural. It willibe 'se en'th at in some-cases a certain proportion of the heptane extract was in'corporated-in-the suspendingoil. The l heptane extract was that obtained by prior washing o f the particulate asphalt with heptane so as to remove approximately by weight of the original asphalt, thus providing the particles with a surface deficiency in maltenes, e. g., high in asphaltenes and resistant to dissolution in the suspending oil. The properties of the plastisols employing part of the heptane extract indicates that the latter is useful in obtaining asphalt compositions having desired properties. In order to alter the properties of the finally coalesced composition, the proportion of heptane (or other) extract may be varied so as to employ the entire amount of extract or any fraction thereof; alternatively, a greater amount of maltenes may be incorporated in the blending oil than that extracted from the treated particles.

zandysabo'ut 13,00 tSUS at "210 F, the composition -so prepared comprising 40-60% by Weight 0f lsusp'ended asphalttparticles and .60-'40% byweight .of the suspending oil.

2..A.process"of'forming a bituminous plastisol which comprises "washing :pulverulent bituminous material -having'anz'average particle size between about 0.5 micron and about 200 microns with an aliphatic hydrocarbon 'havi'ngfrom about 3 to'about 10 carbon atoms per-molecule for a periodandat atemperaturesufficient to superficially remove -malten'es from the surface thereof and subsequently "-susperidin'g'the washed-product in a petroileum fraction in the lubricating oil range, said oil having an'arOmatic hydrocarbon'content from about 15% to about and having aviscosity'between about 100 SUS at'100" Fsand about.300 SUS at 210 F., the'com- :pdsition-so :prliared comprising 40-60% by weight of suspended asphaltparticles and 60'40% by weight of the suspending oil.

3. A process of forming an asphalt plastisol 'Which comprises washing'a -pulverul'ent asphalt having an average particle sizes-of 5-75 microns with a lower alkane at a (temperature betweenabout 15 C. and about -C. fortia'tim'e sufiicient'to,substantially reduce the maltene 'content ofthesurifa'cesofsaid asphalt and thereafter susipenclin'g'the washed powderin a petroleum fraction in the lubricating -oil. range:having an aromatic hydrocarbon content between about 15% and about 60% and a viscosity between about SUS at 100 F. and about 300 SUS at 210 F., said fraction being one which will not dissolve the Washed powder at ordinary temperatures, but which will dissolve it at elevated temperatures, the composition so prepared comprising 40-60% by weight of suspended asphalt particles and 60-40% by weight of the suspending oil.

4. A process of forming an asphalt plastisol which comprises washing a purverulent asphalt having an average particle size of 5-75 microns with a lower 'alkane at a temperature between about 15 C. and about 75 C.

TABLE III Properties of blown type plastisols Composition of Plastiosols Prlgpentiesl of Properties of Asphalt as ISO Blending Agent Brookfield Vise, at Percent Percent 77 F. Poises Pen. at Softening Penetra- Washed Heptane 77 F. Point, tion Pitch Extract F. lndex Material Percent Initial After 7 w. days Bulk Dist., 60 SUS at 210 F 20 {1 1 5 ami set fs i 136 14 245 5 1S a 40. s 14. 2 {gawk gg s fi S t i1 300 24 201 4. 3

ist., 2 a e 37. 1 12. 9 D 2 g S,fi fi g2 330 43 3. 1

111 is 0 a 10- 39. s 12. 2 {Motor Ramate, 24 570 27 200 4. 5 50 Low Vise. Index, 750 Distillate 50 106 14 220 4. 3 45. 9 14. 1 380 Distillate, dewaxed 40 22 233 5. 8

1 From extraction furfural of 100 SUS at 210 F. Bulk Distillate.

Based on Flash Cracker Pitch, 31 average particle size, washed at 115 F. with 3 cc n-heptane per gram pitch; extract ca 25% w.

We claim as our invention:

1. A process of forming a bituminous plastisol which comprises washing pulverulent bituminous material having an average particle "size between about 0.5 micron and about 200 microns with normal heptane for a period and at a temperature sufficient to superficially remove maltenes from the surface thereof and subsequently suspending the washed product in a petroleum fraction in the lubricating oil range, said oil having an aromatic hydrocarbon content from about 15% to about 60% for a time sufficient to substantially reduce the maltene content of the surfaces of said asphalt and thereafter suspending the washed powder in petroleum fraction in the lubricating oil range having an aromatic hydrocarbon content between about 15% and about 60% and a viscosity between about 100 SUS at 100 F. and about 300 SUS at 210 F., said fraction being one which will not dissolve the Washed powder at ordinary temperatures, but which Will dissolve it at elevated temperatures, said petroleum fraction having added thereto at least and having a viscosity between about 100 SUS at 100 75 a portion of the maltenes removed during the initial 11 washing step, the suspended washed particles constituting 40-60% by weight and the suspending oil phase con stituting 6040% by weight.

5. A process according to claim 4 wherein the lubrieating oil contains from about 15% to about 30% aromatic hydrocarbons, whereby a plastisol capable of forming a roofing grade asphalt composition is provided.

6.'A process according to claim 4 wherein the lubricating oil contains from about 30% to about 60% aromatic hydrocarbons, whereby a plastisol capable of forming a paving grade asphalt composition is provided.

7. An asphalt plastisol composition comprising 6040% by weight of a hydrocarbon oil of lubricating oil viscosity having an aromatic hydrocarbon content between about 15% and about 60% by weight, having suspended therein 40-60% by weight of asphaltic particles having an average diameter between about 0.5 micron and about 200 microns, the surfaces of said particles being lubricating oil-resistant, the asphalt beneath the surface of said particles being more readily dissolved in the suspending oil than the surfaces thereof.

8. A process of forming an asphalt plastisol comprising providing pulverulent asphalt with a superficial lubricating oil-resistant oxidized asphalt coating, heating said coated particles for a time suflicient to substantially reduce the surface area of the individual particles and close the surface pores thereof, and suspending the coated and treated particles in a lubricating oil having an aromatic hydrocarbon content? between about 15% and about whereby a plastisol is formed.

9. A composition according to claim 7 wherein the asphalt particles have an ASTM'penetratiOn at 77 F. of 0-5.

10. A composition according to claim 9 wherein the asphalt particles have a softening point of -240 E.

,11. A composition according to claim 7 wherein the surfaces of the particles comprise blown asphalt.

12. A composition according to claim 7 wherein the surfaces of the particles have a substantially greater proportion of asphaltenes than the asphalt beneath the surfaces.

References Cited in the file of this patent UNITED STATES PATENTS 205,750 Johns July 9, 1878 727,506 Warren May 5, 1903 1,077,081 Kaempf Oct. 28, 1913 2,131,205 Wells et al Sept. 27, 1938 2,200,484 Batchelder May 14, 1940 2,308,245 Ortynsky Jan. 12, 1943 2,366,657 Sorem Jan. 2, 1945 2,399,717 Arveson May 7, 1946 2,572,744 Mollring Oct. 23, 1951 2,661,300 Romberg et a1. Dec. 1, 1953 

1. A PROCESS OF FORMING A BITUMINOUS PLASTISOL WHICH COMPRISES WASHING PULVERULENT BITUMINOUS MATERIAL HAVING AN AVERAGE PARTICLE SIZE BETWEEN ABOUT 0.5 MICRON AND ABOUT 200 MICRONS WITH NORMAL HEPTANE FOR A PERIOD AND AT A TEMPERATURE SUFFICIENT TO SUPERFICIALLY REMOVE MALTENES FROM THE SURFACE THEREOF AND SUBSQUENTLY SUSPENDING THE WASHED PRODUCT IN A PETROLEUM FRACTION IN THE LUBRICATING OIL RANGE, SAID OIL HAVING AN AROMATIC HYDROCARBON CONTENT FROM ABOUT 15% TO ABOUT 60% AND HAVING A VISCOSITY BETWEEN ABOUT 100 SUS AT 100* F. AND ABOUT 300 SUS AT 210*F., THE COMPOSITION SO PREPARED COMPRISING 40-60% BY WEIGHT OF SUSPENDED ASPHALT PARTICLES AND 60-40% BY WEIGHT OF THE SUSPENDING OIL. 